In a semiconductor manufacturing process, CMP (Chemical Mechanical Polishing) is performed with a polishing apparatus to planarize a surface of a wafer. In CMP, the polishing apparatus polishes the wafer with a polishing head while pressing the wafer against a polishing pad. The polishing apparatus is provided with a retainer ring that surrounds the wafer in order to suppress deviation of the wafer with respect to the polishing head and to prevent the wafer from coming out.
In a conventional polishing apparatus, however, a radial gap between the retainer ring and the wafer generates rebound (rise) of the polishing pad in the radial gap. The generated rebound causes overpolishing in an outer peripheral edge portion of the wafer.
Further, while the polishing pad and the polishing head are rotated in the same direction in CMP, conventionally, polishing proceeds in a state where the wafer is shifted toward a downstream side in a rotation direction of the polishing pad. This increases variation in a polishing amount in a circumferential direction of the wafer.